1. Field of the Invention
The present invention relates to a rotary operation mechanism, and to an electronic apparatus and a projector that are equipped with a rotating operator for effecting rotary operation of a rotary member such as a variable resistor.
2. Description of the Related Art
Some electronic apparatuses are provided with rotary operation mechanisms having rotating knobs for performing various operations. In one known form of this type of rotary operation mechanism, a mechanism in which a rotating knob for operating the main unit of the apparatus is arranged on the outer case that covers the main body of the electronic apparatus.
As a rotary operation mechanism of the prior art, Japanese Patent Laid-Open Publication No. 144564/99 discloses a configuration that is provided with a rotary electronic component that is provided on a printed wiring board and a rotary operator for realizing rotary operation of this rotary electronic component; and in which the rotary operator is composed of a first operation member that is freely rotatably installed in an opening of the case and a second operation member that is assembled with the first operation member.
Conventionally, when a rotating knob is arranged on the exterior of an outer case for realizing the rotary operation of an internal rotating part such as an adjustment gear or a rotary variable resistor that is provided inside the main unit of an electronic apparatus, the following various structures have been adopted while taking into consideration such issues as: divergence in the relative position of the internal rotating part and the rotating knob that accompanies error in the assembly of the apparatus main unit and the outer case; the design of the external appearance of the outer case; the feel of operating the rotating knob; and the workability of assembly.
(i) In a configuration in which a substantially cylindrical engagement part is formed on a rotating knob and in which this engagement part is freely rotatably engaged in an opening of the outer case, an opening is provided having an inside diameter that is somewhat greater than the outside diameter of the engagement part of the rotating knob, and the rotating knob is arranged to project toward the outside of the outer case such that the outer periphery of the rotating knob overlaps the opening of the outer case to thereby conceal the opening in the outer case from view from the outside.
(ii) Engaging and supporting a rotating knob on the outer case side secures a relatively large clearance, this clearance being the gap when the rotating knob is imposed upon the internal rotating part.
(iii) A large clearance is maintained between a rotating knob and the opening in an outer case such that the rotating knob does not rub against the inside of the opening in the outer case even when divergence occurs in the relative position of the rotating knob and the internal rotating part.
(iv) After accurately positioning and attaching rotating knobs with respect to the openings of an outer case, the internal rotating parts are secured one by one.
However, despite the adoption of the above-described measures (i)-(iv) in a rotary operation mechanism of the prior art, several problems occur.
Specifically, in a rotary operation mechanism of the prior art, when priority is given to preventing divergence in position between a rotating knob and the opening of the outer case, a greater amount of clearance must be secured between the rotating knob and the internal rotating part. As a result, when rotating the rotating knob, the problem arises that the rotating knob exhibits idle movement and play with respect to the internal rotating part.
On the other hand, if priority is given to eliminating any free play of the rotating knob and the rotating knob is assembled with minimum clearance with respect to the internal rotating part, a large amount of clearance must be secured between the rotating knob and the opening in the outer case, and the problem therefore arises that divergence occurs in the positions of the rotating knob and the opening.
This divergence in position of the rotating knob with respect to the opening can be made less noticeable by arranging the rotating knob to project away from the outer case. However, this solution imposes limitations on the outside design of the outer case.
Accordingly, for absorbing the assembly error between the outer case and the apparatus main unit and allowing smooth and binding-free rotation of a rotating knob inside the opening in the outer case, this rotating knob being assembled with an internal rotating part provided in the apparatus main unit, necessitates the sacrifice of either the feel of operating the rotating knob or the outside design of the outer case.
Alternatively, after accurately positioning the rotating knob with respect to the opening in the outer case, the rotating knob must be imposed on the internal rotating part. This solution results in an assembly having poor workability and a high rate of assembly defects. These problems become particularly significant when a plurality of rotating knobs is provided for allowing rotary operation of a plurality of internal rotating parts.